One of the major factors in the froth flotation of ores is to provide value mineral concentrations which have as low levels of gangue minerals as possible. When sulfide ores are used, for example, flotation concentrates are transported directly to smelting without additional processing and therefore major concentrations of gangue contaminants therein result in the production of sulfur waste products and SO.sub.2 atmospheric pollution which are detrimental to the environment. The problem is becoming so prevalent that smelters are willing to sacrifice the value mineral concentration of feeds if the gangue sulfide concentration is also lower.
It has now been found that certain synthetic polymers containing a combination of certain functional groups are very effective depressants for the separation of certain value minerals from other value minerals and/or from gangue minerals, in general, and pyrite, pyrrhotite and other gangue sulfides, in particular. These depressants result in a substantial reduction of the gangue minerals contamination of mineral concentrates which are transported to the smelter thereby, especially in the case of sulfide mineral concentrates, having a positive effect on the environmental impact of the smelting operation. The term "gangue", as used herein, may include the so-called penalty elements such as arsenic and antimony, especially as sulfides.
U.S. Pat. No. 4,866,150 is directed to novel copolymers and terpolymers of an acrylamide and a thiourea which are taught as depressants for gangue sulfide minerals whereas U.S. Pat. No. 4,888,106 claims the use of those polymers in the beneficiation of value sulfide minerals.
U.S. Pat. No. 4,744,893 claims a method for beneficiating value sulfide minerals using a depressant comprising a terpolymer of an acrylamide, a hydroxyl group containing monomer and an acrylic acid or salt. The polymer per se is claimed in U.S. Pat. No. 4,902,764.